DeleteMiddleElementFromStack.java

package RecursionAndBacktracking;
/*
* We have given a stack containing numbers we have to delete the middle element present in the stack.
* Middle element is present at position : (stack.size() / 2 + 1)
*/
import java.util.Scanner;
import java.util.Stack;

public class DeleteMiddleElementFromStack {
 private static void deleteMiddle(Stack<Integer> stack, int k){
 // Base condition
 if(stack.size() == 0)
 return;
 solve(stack, k);
 }
 public static void solve(Stack<Integer> stack, int k){
 // Base condition : if k==1 it means that the top element is the deleting element which we have to delete
 if(k == 1){
 stack.pop();
 return;
 }
 // else
 int val = stack.pop();
 solve(stack, k-1);
 stack.push(val);
 }
 public static void main(String[] args) {
 Scanner sc = new Scanner(System.in);
 System.out.println("Enter the number of test cases:");
 int t = sc.nextInt();

 while (t-- > 0) {
 System.out.println("Enter elements: if want to stop enter -1");
 Stack<Integer> stack = new Stack<>();
 int ele = 0;
 ele = sc.nextInt();
 while (ele != -1){
 stack.push(ele);
 ele = sc.nextInt();
 }
 int k = stack.size()/2 + 1;
 deleteMiddle(stack, k);
 System.out.println(stack);
 }
 }
}